A tire manufacturing system, particularly a molding system for molding a green tire has been increasingly sophisticated and complicated recently to respond to a request for upgrading of a tire quality and improvement of productivity, and improvement of tire manufacturing capacity while restraining an occupied space and a cost of a molding system is in demand. Therefore, instead of provision of a plurality of conventional tire molding machines for assembling various tire component members at a single place, a plurality of working stations where tire component members are assembled according to them are provided and a molding system for conveying a tire being molded between these stations at a predetermined tact time is used. But with this molding system, it is difficult to switch and assemble tire component members corresponding to plural sizes at each station within a predetermined tact time, and small-lot production can not be supported since tires in mixed different sizes can not be molded continuously, which extremely limits its practical application.
In order to solve this problem, as disclosed in the International Publication WO 01/39963, a system capable of continuous molding of a group of tires in mixed plural sizes is proposed, and this molding system comprises the steps of assembling each tire component members on a rigid core with the cross section in the toroidal shape, forming a green tire on the rigid core, vulcanizing the tire while being mounted on the rigid core and taking the cured tire out of the rigid core at the last stage.
However, this molding system has the following problems. First, structural change from the conventional tire is inevitable since members are assembled on the rigid core, and since the conventional structure in which one or more layers of carcass ply is rolled up around each bead core outward in the tire radial direction can not be used, a new tire structure so as to fix the carcass onto the bead core should be employed, but reliability of this new tire structure has not been fully established yet.
The second problem is, a rigid core used both in molding a green tire and vulcanizing the molded green tire should be held at a room temperature in the molding process but the temperature should be raised in the vulcanizing process. Therefore, energy and time for heating and cooling the rigid core is wasted.
The present invention has been made in view of the above problems and has an object to provide a tire manufacturing method in which tires in mixed plural sizes can be molded continuously by moving the tire being molded between working stations and moreover, the conventional tire structure does not have to be largely changed or energy and time can be prevented from being wastefully consumed.